1. Field of the Invention:
This invention relates to a fabrication method for a field emission display (FED) emitter, and more particularly to a fabrication method by photolithography and etching for a FED emitter.
2. Description of Related Art:
Currently, flat panel display technology includes cathode ray tube (CRT), thin film transistor liquid crystal display (TFTLCD), plasma display panel (PDP), and FED, some of which have been successfully applied in the market. The FED is expected to be one of the more strongly competitive displays used in the 21.sup.st century. The FED is composed of a pair of upper and lower plates. A number of spacers are located in between the upper plate and the lower plate. The upper plate, serving as an anode plate, usually is a glass plate coated with a phosphorus material. The lower plate, serving as a cathode plate, is usually a field emission array (FEA), which can emit an electron beam. A gate between the anode plate and the cathode plate regulates the flux of the electron beam. When emitted electrons pass the gate, they are accelerated by the electric field in order to gain enough energy to hit the phosphorus material. A catho-luminescent phenomenon results.
The FEA applied in current FEDs is basically a type of tip emitter or thin film edge emitter. The array is composed of a number of pixels in a matrix structure; each pixel has its own matrix address. Every pixel further includes several hundred spikes or thin film edges. The spike root is about 1 micron and the tip of the spike has a radius of about less than 0.1 micron. The spikes are made of metal, such as molybdenum (Mo), tungsten (W), or platinum (Pt), or a semiconductor material, such as silicon or diamond.
FIGS. 1A-1C are cross sectional views schematically illustrating the fabrication flow of a conventional tip emitter using metal material.
Referring to FIGS. 1A-1C, an oxide layer 102 is formed over a substrate 100, and a photoresist layer 104, with an opening, is formed over the oxide layer 102. A groove 106 corresponding to the opening of the photoresist layer 104 is formed on the oxide layer 102 through isotropic etching. The groove 106 exposes the substrate 100. The isotropic etching includes wet etching using, for example, a HF acid solution. Due to the isotropic etching, the groove 106 has a wider aperture than the opening of the photoresist layer 104 so that the photoresist layer 104 around the opening region overhangs a portion of the groove 106. In this structure, after a metal, such as Mo, W, or Pt, is sputtered on the substrate, a spike 108 with sharp tip is formed on the substrate. This is called a shading effect. After sequentially removing the photoresist 104 and the oxide layer 102, only the spike 108 remains on the substrate 100.
FIGS. 2A-2C are cross sectional views schematically illustrating the fabrication flow of a conventional tip emitter using silicon.
Referring to FIGS. 2A-2C, a photoresist layer 202 with an opening is formed over a silicon substrate 200. Usingi the photoresist layer 202 as an etching mask, the silicon substrate 200 is etched to form a V-shaped groove 204, in which the V-shape is formed due to the properties of the silicon material. After removing the photoresist layer 202, an oxide layer 206 is formed over the substrate. Then, a silicon layer 208 is deposited over the oxide layer 206 which also fills the V-shape groove 204. After removing the oxide layer 206, the silicon layer 208 is separated from the silicon substrate 200. The silicon layer 208 therefore carries a triangle spike 208a, which is conformal with the V-shape groove 204.